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International Journal of Advances in Engineering & Technology, Mar. 2014.
©IJAET
ISSN: 22311963

A FUZZY LOGIC CONTROLLER OF THREE-PHASE SHUNT
ACTIVE FILTER FOR HARMONIC CURRENT COMPENSATION
Kouadria Mohamed Abdeldjabbar, Allaoui Tayeb, Belfedal Cheikh
Laboratoryof Electrical and Computer Engineering (L2GEGI),
Ibn Khaldun University, Tiaret, Algeria

ABSTRACT
Performance investigation of Shunt Active Power Filter for harmonic elimination is an interdisciplinary area of
interest for many researchers. This paper presents performance improvement of 3-phase Shunt Active Power
Filter (SAPF) with Hysteresis Current Control technique for elimination of harmonic in a 3-phase distribution
system. The shunt active filter employs a simple method called synchronous detection technique for reference
current generation. A proportional-integral (PI) and Fuzzy Logic Controller (FLC) are designed to adjust the
parameters of the SAPF system. The proposed system has achieved a low Total Harmonic Distortion (THD)
which demonstrates the effectiveness of the presented method. The simulation of global system control and
power circuits is performed using Matlab-Simulink and Sim Power System toolbox. The simulation results
presented demonstrate improved performance of the SAPF system with the proposed fuzzy logic control
approach.

KEYWORDS: Power quality, Shunt active filter, Synchronous Detection Method (SDM), hysteresis control, PI
controller, Fuzzy logic controller, total harmonic distortion (THD).

I.

INTRODUCTION

Power Quality is a set of electrical limitations that allows a piece of equipment to function in its
intended manner without significant loss of performance or life expectancy [1]. The harmonics
presence in the power lines results in varied problems, like, greater power losses in distribution;
problems of electromagnetic interference in communication systems; and operation failures of
protection devices, electronic equipments and, industrial processes. The Active filters have been
recognized as a valid solution to harmonic and reactive power compensation due to the presence of
non-linear loads. The principle of operation of active filters is based on the injection of the harmonics
required by the load. An active filter generates a current equal and opposite in polarity to the
harmonic current drawn by the load and injects it to the point of coupling and forces the source
current to be pure sinusoidal. As a consequence, the characteristics of the harmonic compensation are
strongly dependent on the filtering algorithm employed for the calculation of load current harmonics
[2]
The shunt APF is designed to be connected in parallel with the nonlinear load. It detects the harmonic
current of nonlinear load and injects into the system a compensating current, identical with the
nonlinear load harmonic current but in opposite phase. Therefore, the net current drawn from the
distribution network at the point of coupling of filter and the load will be a sinusoidal current of only
fundamental frequency[3][4]. The current compensation characteristic of the shunt active power filter
is shown in Fig.1.

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Vol. 7, Issue 1, pp. 82-89

International Journal of Advances in Engineering & Technology, Mar. 2014.
©IJAET
ISSN: 22311963

Figure 1. Compensation characteristics of a shunt active power filter

In the present paper, the three-phase shunt active filter based on fuzzy logic current controller is
proposed to compensate current harmonics. The new controller is designed to improve compensation
capability of SAPF by adjusting the DC voltage error using a fuzzy rule. The reference current signals
required to compensate current harmonics use the synchronous reference detection method. The
performances of the proposed SAPF are evaluated through computer simulations for transient and
steady-state conditions with nonlinear loads using Matlab-Simulink program and SimPowerSystem
toolbox.

II.

CONTROL STRATEGIES

Different control algorithms are proposed for APF but a Synchronous detection method is used for
harmonic detection to calculate reference current for shunt active power filter due to its simplicity.
The balanced three phase source currents can be obtained after compensation. The equal current
distribution method of this control scheme is implemented in this research work. The following steps
are used for generation of reference signal [11].

Figure 2.SAPF tuned with SDM method

Hypothesis for this method is

I sa  I sb  I sc

(1)

Where I sa , I sb and I sc represent the peak values of source current in phase a, b and c respectively.
Voltage and current expression can be written as follows: 3-phase source voltages are given by

83

Vol. 7, Issue 1, pp. 82-89

International Journal of Advances in Engineering & Technology, Mar. 2014.
©IJAET
ISSN: 22311963

Vsa (t )  Vma sin wt
Vsb (t )  Vmb sin( wt  120 )

(2)

Vsc (t )  Vmc sin( wt  240 )
3-phase current drawn by load given by


I La (t )   I an sin( wt  an )
n 1


I Lb (t )   I bn sin( wt  bn  120 )

(3)

n 1


I Lc (t )   I cn sin( wt  cn  240 )
n 1

The 3-phase instantaneous power (p 3φ) in the proposed system can be written as

p3  vsaiLa  vsbiLb  vsciLc
p3  pa  pb  pc


 Vma sin wt  I an sin( wt  an ) 
n 1



Vmb sin( wt  120 ) I bn sin( wt  bn  120 ) 

(4)

n 1


Vmc sin( wt  240 ) I cn sin( wt  cn  240 )
n 1

The instantaneous power is passed through low pass filter (LPF), which blocks higher order frequency
component and only fundamental component is obtained from the output of LPF.

p fund  Vma sin wtI a1 sin( wt  a1 )  Vmb sin( wt  120 ) I b1 sin( wt  b1  120 ) 
Vmc sin( wt  240 ) I c1 sin( wt  c1  240 )


Vma I a1
V I
cos a1  cos(2wt  a1 )  mb b1 cos b1  cos(2wt  b1 ) 
2
2
Vmc I c1
(5)
cos c1  cos(2wt  c1 )
2

The average fundamental power in 3-phase is given by
T

pav   p fund dt
0



Vma I a1
V I
V I
cos a1  mb b1 cos b1  mc c1 cos c1
2
2
2

(6)

For 3- phase balanced nonlinear load the followings can be written as

Vma  Vmb  Vmc  V
I a1  Ib1  I c1  I

a1  b1  c1  1
3VI
cos 1
(7)
2
Using equation (7), average power per phase can be written as
VI
( pav ) ph 
cos 1
(8)
2
pav 

84

Vol. 7, Issue 1, pp. 82-89

International Journal of Advances in Engineering & Technology, Mar. 2014.
©IJAET
ISSN: 22311963
Let Icos1  I m  Maximum amplitude of per phase fundamental current

Im 

2( pav ) ph
V

(9)

The fundamental current is given by

I Fa (t )  I m sin wt
I Fb (t )  I m sin( wt  120 )

(10)

I Fc (t )  I m sin( wt  240 )
The expression of reference current for shunt active power filter in each phase (i*ca, i*cb, i*cc )

i *ca  I La  I Fa
i *cb  I Lb  I Fb
i *cc  I Lc  I Fc

After getting the reference current, it is compared with the actual current by using hysteresis current
comparator to generate six switching pulses, which are used to control the IGBT either by turning ON
or OFF.

III.

CONTROLLER DESIGN

3.1. PI Controller
Fig.3 shows the internal structure of the control circuit. The control scheme consists of PI controller,
limiter, and three phase sine wave generator for reference current generation and generation of
switching signals[10]. The peak value of reference currents is estimated by regulating the DC link
voltage. The actual capacitor voltage is compared with a set reference value [5].

Figure 3 Conventional PI Controller

3.2. fuzzy logic controller
Among the various power filter controller, the most promising is the fuzzy logic control. A fuzzy
controller consists of stages: fuzzification, knowledge base, inference mechanisms and
defuzzification.
The knowledge bases designed in order to obtain a good dynamic response under uncertainty in
process parameters and external disturbances [6][7].
In this study the fuzzy logic controller is used to control the DC capacitor voltage. The capacitor
voltage deviation and its derivative are considered as the inputs variables of the FLC and the control
voltage vdc present the output as shown in figure.4 [8].

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Vol. 7, Issue 1, pp. 82-89

International Journal of Advances in Engineering & Technology, Mar. 2014.
©IJAET
ISSN: 22311963

Figure 4 ConventionalFuzzy LogicController

The input and output variables are converted into linguistic variables. We have chosen seven Fuzzy
subsets, NL(Negative), EZ (Environ Zero) and P (Positive). In this paper, we have applied min-max
inference method to get implied fuzzy set of the turning rules and the “centroid” method was
used to deffuzzify the implied fuzzy control variables.
The membership functions used for the input and output variables are shown in figure.5, the Fuzzy
rule base is given in the tabe.1 [9].

Figure 5Membership function for theinput and output variables

86

Vol. 7, Issue 1, pp. 82-89

International Journal of Advances in Engineering & Technology, Mar. 2014.
©IJAET
ISSN: 22311963
Table.1 Fuzzy control rule:

IV.

Ei
∆Ei

N

EZ

P

N
EZ
P

N
N
EZ

N
EZ
P

EZ
P
P

SIMULATION RESULTS AND DISCUSSION

The simulation results are provided to verify the performance and effectiveness of the proposed
control scheme based on fuzzy current controller for the shunt active power filter compared to
conventional PI controller. The parameters of the simulation are: Lf = 3 mH, C1 =2200 μF, Vs =220
V/50 Hz, and Vdc-ref = 700 V.

4.1. Simulation results using PI controller
Fig. 6 shows the simulated waveforms of three-phase ac source voltages and source current before
compensation.
The waveforms of source voltage and source current after compensation are simultaneously shown in
Fig. 7. The DC voltage is presented in Fig. 8.
200

300

150
200

Source Voltage (V)

Load current (A)

100
50
0
-50

100

0

-100

-100
-200

-150
-200
0.2

0.22

0.24

0.26

0.28

0.3
0.32
Time (S)

0.34

0.36

0.38

-300
0.2

0.4

0.22

0.24

0.26

0.28

0.3
0.32
Time (S)

0.34

0.36

0.38

0.4

Figure 6. Source voltages and source current without APF

710

200
150

700

690

50

Vds (V)

Source Current (A)

100

0

680

-50
670

-100
660

-150
-200
0.2

0.22

0.24

0.26

0.28

0.3
0.32
Time (S)

0.34

0.36

0.38

0.4

Figure 7.Source current after compensation using PI controller

650

0

0.5

1

1.5
Time (S)

2

2.5

Figure8. DC side capacitor voltage

4.2. Simulation results using fuzzy controller
The source current before APF application using fuzzy controller is shown in Fig. 9.
The waveforms of source current after compensation is shown in Fig. 18. Lastly, the output DC
capacitor voltage is presented in Fig. 11.

87

Vol. 7, Issue 1, pp. 82-89

3

International Journal of Advances in Engineering & Technology, Mar. 2014.
©IJAET
ISSN: 22311963
200
150

Load Current (A

100
50
0
-50
-100
-150
-200
0.2

0.22

0.24

0.26

0.28

0.3
0.32
Time (S)

0.34

0.36

0.38

0.4

Figure 9.source current without APF
200

710

150
700

Source Current (A)

100
690

Vdc (V)

50
0

680

-50
670

-100
660

-150
-200
0.2

0.22

0.24

0.26

0.28

0.3
0.32
Time (S)

0.34

0.36

0.38

0.4

Figure 10.Source current after compensation using Fuzzy controller
voltage

V.

650

0

0.5

1

1.5
Time (S)

2

2.5

Figure11. DC side capacitor

CONCLUSION

In the present paper, a three-phase three-level shunt active filter with neutral-point diode clamped
inverter based on fuzzy logic current controller is presented. Use of the filter is aimed at achieving the
elimination of harmonics introduced by nonlinear loads. Several simulations with various nonlinear
loads (AC/DC converter with R,L) under different conditions are performed using the conventional PI
and fuzzy current controllers. The results show the superiority and effectiveness of the proposed fuzzy
controller in terms of eliminating harmonics and response time, The THD is significantly reduced
from 23.74% to 4.12% by conventional PI controller and to 3.26% for fuzzy controller (with APF) in
conformity with the IEEE standard norms. The current source for the two controllers after
compensation is sinusoidal. Hence, the proposed fuzzy logic current controller is an excellent
candidate to control shunt active filters based on inverter topology to eliminate the harmonic currents
without scarifying performance tracking as compared to PI controller.

REFERENCES
[1]. H. Akagi, “New Trends in Active Filters for Power Conditioning,” IEEE Trans. on Industry
Applications, vol. 32, no. 6, pp. 1312-1322, 1996.
[2]. M. George and K. P. Basu, “Three-phase shunt active power filter,”American Journal of Applied
Sciences, vol. 5 (8), pp. 909–916, 2008.
[3]. S. K. Jain, P. Agrawal and H. O. Gupta, “Fuzzy logic controlled shunt active power filter for power
quality improving”, IEE Electr Power Appl, 149(5):317-328, 2002.
[4]. G. K. Singh, A. K. Singh, R. Mitra, “A simple fuzzy logic based robust active power filter for
harmonics minimization under random load variation”, Electr Power SystReseach, 77:1101-1111,
2007.

88

Vol. 7, Issue 1, pp. 82-89

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International Journal of Advances in Engineering & Technology, Mar. 2014.
©IJAET
ISSN: 22311963
[5]. M.I.M. Montero, E.R. Cadaval, F.B. Gonzalez, “Comparison of control strategies for shunt active
power filters in three-phase four wire systems”, IEEE Transactions on Power Electronics, Vol. 22, No.
1, pp. 229-236, 2007.
[6]. Hamadi A, El-Haddad K, Rahmani S, Kankan H (2004) Comparison of fuzzy logic and proportional
integral controller of voltage source active filter compensating current harmonics and power factor.
IEEE IntConfIndTechnol 2:645–650
[7]. T. Georgios, and A. Georgios , “Shunt active power filter control using
fuzzy logic controllers”,
IEEE International Symposium on Industrial Electronics (ISIE), pp. 365 – 371, 2011.
[8]. FMd.AshfanoorKabil and UpalMahbub, " Synchronous detection and Digital control of Shunt Active
Power Filter in Power Quality Improvement " , IEEE Conference on Power and Energy Conference at
Illinois (PECI 2011) , pp 1-5, Nov 2011.
[9]. S.K.Jain, P.Agrawal and H.O.Gupta, Fuzzy Logic controlled shunt active power filter for power
quality improvement, IEE proceedings in Electrical Power Applications, Vol 149, No.5, September
2002.
[10]. S. Jain, P. Agarwal, &H.O.Gupta, "A control algorithm for the compensation of customer generated
harmonics and reactive power", IEEE Trans. On Power Delivery, Vol. 19, No.1, Jan 2004,pp 357366N. Mendalek, K. Al-Haddad, F. Fnaiech and L. A. Dessaint,” Nonlinear control technique to
enhance dynamic performance of a shunt active power filter,” Proc. IEE Elec. Power App., vol. 4, pp.
373-379, July 2003.

AUTHORS
KOUADRIA Mohamed abdeldjabbar is PhD student in the Department of Electrical
Engineering in at the Ibn Khaldoun University of Tiaret, ALGERIA. He received a
MASTER degree in Automation and control of industrial systems from the UIK of Tiaret.
His research activities include the Renewable Energies and the Control of Electrical
Systems. He is a member in Energetic Engineering and Computer Engineering Laboratory
(L2GEGI)

ALLAOUI Tayeb received his engineer degree in electrical engineering from the Ibn
Khaldoun University of Tiaret in 1996 and his master degree from the University of Science
and Technology of Oran in 2002.His research interests includes intelligent control of power
systems and FACTS, Active filter and renewable energies. He is a Director of Energetic
Engineering and Computer Engineering Laboratory (L2GEGI).

BELFEDAL Cheikh received the Magister degree in electrical engineering from Tiaret
University, Algeria, in 1996. Currently he is with the Department of Electrical Engineering,
Tiaret University. His fields of interest are control of electrical machines, power converters,
modelling and control of wind turbines. He is a member in Energetic Engineering and
Computer Engineering Laboratory (L2GEGI)

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